Microparticles, microcapsules and microspheres have important applications in the medical, pharmaceutical, agricultural, textile and cosmetics industries as delivery vehicles, cell culture substrates or as embolization agents.
Polymeric microspheres, i.e., microspheres formed (at least in part) from a crosslinkable polymer, have found a variety of uses in the medical and industrial areas. They may be employed, for example, as drug delivery agents, tissue bulking agents, tissue engineering agents, and embolization agents. Accordingly, there are numerous methods directed toward preparing polymeric microspheres. These methods include dispersion polymerization of the monomer, potentiometric dispersion of a dissolved crosslinkable polymer within an emulsifying solution followed by solvent evaporation, electrostatically controlled extrusion, and injection of a dissolved crosslinkable polymer into an emulsifying solution through a porous membrane followed by solvent evaporation.
Additional methods include vibratory excitation of a laminar jet of monomeric material flowing in a continuous liquid medium containing a suitable suspending agent, irradiation of slowly thawing frozen monomer drops, and continuous injection of a dissolved crosslinkable polymer into a flowing non-solvent through a needle oriented in parallel to the direction of flow of the non-solvent.
These methods known in the art have shortcomings that may curtail the formation of uniformly sized microspheres of small diameter ranges (e.g., in the range of 100-600 microns) for various applications, particularly when the base material has a high viscosity.